1. Field of the Invention
The present invention relates to a vehicular microwave detector which is mounted in general automobiles to emit an alarm to the driver upon detecting a prescribed microwave that reaches the detector from the outside, and in particular relates to a vehicular microwave detector which is powered by a solar cell panel and secondary battery provided in the detector.
2. Description of the Prior Art
Vehicular microwave detectors which are mounted to the dashboard or front windshield of an automobile by a pressure sensitive adhesive sheet or suction cup are well known in the prior art as a means of generating an alarm upon detecting the microwaves emitted by a laser type speed measuring device. The circuit structure of such detectors are equipped with a horn antenna and a super-heterodyne type receiving circuit at the front end, with control being carried out by a microcomputer, so that when a prescribed microwave band is discriminated an alarm is generated by means of a buzzer, LED lamp or the like.
Shown in FIG. 1 is the structure of a representative example of a type of prior art vehicular microwave detector equipped with a solar cell panel and secondary battery as a power source. As shown in the same drawing, the device comprises a device main body 1 constructed from a flat case and a vehicle interior mounting bracket 2 which can be removably coupled with the underside of the device main body 1. The bracket 2 is equipped with a base plate 21 which is fixed to a surface inside an automobile such as the surface of the dashboard or the inside surface of the front windshield, a connecting plate 22 which can be removably linked with a connecting mechanism 11 integrally formed in the underside case of the device main body 1, and a joint mechanism 23 which links the connecting plate 22 with the base plate 21. In this connection, FIG. 1(A) shows the device main body 1 and the bracket 2 in a coupled state, and FIG. 1(B) shows these elements in a separated state.
Inside the device main body 1, a main circuit substrate 3 is arranged along the bottom surface of the case, with an aperture portion of the horn antenna installed in this main circuit substrate 3 provided so as to face one side surface of the main body case. Further, a solar cell panel 5 is arranged along the case front surface of the device main body 1 so as to be exposed to outside light, whereby the solar cell panel 5 and the secondary battery 6 which is charged by the output of the solar cell panel 5 form the power source of the microwave detector. Furthermore, a human interface control portion 7 and a display portion 8 are arranged on the side portion opposite the direction of the horn antenna 4 and the front surface portion of the device main body 1. The control portion 7 is mainly comprised of a key switch panel equipped with a number of keys, and the display portion 8 is equipped with a number of LED lamps. Moreover, although omitted from the drawings, the main circuit substrate 3 is provided with a high frequency circuit for processing signals received from the horn antenna 4 and a signal processing circuit for microcomputer control. Further, the secondary battery 6 of the power source is set in a battery housing portion on the main body circuit substrate 3 inside the device main body 1, with the secondary battery 6 being connected to the solar cell panel 5 and a stabilizing power circuit on the substrate 3.
This type of vehicular microwave detector is generally purchased by a user who installs it in his or her own automobile. There are two main types of base plates 21 for the bracket 2, wherein in the first type the base plate 21 of the bracket 2 is mounted to the dashboard by a pressure sensitive adhesive sheet, and in the second type the base plate 21 is formed with a suction cup which is mounted to the inside surface of the front windshield. The device main body 1 is coupled to the connecting plate 22, and by adjusting the direction by means of the joint mechanism 23, the aperture of the horn antenna 4 can be made to face forward, and the control portion 7 and display portion 8 can be made to face the driver.
In the case of microwave detectors powered by a solar cell panel and a secondary battery, as described above, there is no need to frequently replace batteries as is required for types which use a primary battery. However, because even the secondary battery has a cycle life, it is necessary for such battery to be replaceable. Further, in the case of disposing of an exhausted microwave detectors the battery should be arranged so as to be easy to remove and recover. Thus, from this point of view as well, it is necessary to provide a structure which makes it possible to replace (or remove) the battery.
Now, in the prior art vehicular microwave detector shown in FIG. 1, the secondary battery 6 is set in a battery housing portion above the main circuit substrate 3 inside the device main body 1 and is connected to the solar cell panel 5 and a stabilizing power circuit above the substrate 3. With this structure, it is difficult to carry out an easy installation or removal of the internal battery, which requires removing an assembly screw and separating half of the case of the device main body 1 to expose the inside. In other words, in the example structure shown in FIG. 1, because the main circuit substrate 3 has a large surface area and is arranged below the battery 6, and because the solar cell panel 5 and the key switch panel of the control portion 7 is arranged above the battery 6, installation or removal of the battery 6 can not be carried out without separating half of the case. This results in an extremely troublesome operation.